import sys

class H:
    def __init__(self):
        self.a=1

H90  # name 'H90' is not define

try:
    H90
except:
    a,b,c=sys.exc_info()

a  # class 'NameError
b  # NameError("name 'H90' is not define")
c  # 一个traceback类地址

str(b)  # name 'H90' is not define